This invention relates to marking heads and more particularly to marking heads having rotatable marking wheels.
Marking heads having one and preferably a plurality of rotatable marking wheels are frequently used in various industrial applications to stamp one or a series of numbers or other symbols on a workpiece or part. Typically, a marking head has several rotatably mounted wheels each having a series of numbers or other symbols circumferentially spaced about the periphery of the wheel. Each wheel can be incrementally rotated or indexed to position the desired symbol for use in marking a workpiece. Usually each wheel is indexed or advanced by a pawl which successively engages one of a series of circumferentially spaced teeth of a cogwheel connected to or integral with the marking wheel. The teeth correspond with the array of circumferentially spaced symbols.
When marking relatively hard workpieces such as those made of iron or steel a large force must be applied to the marking head to stamp the numbers or symbols in the workpiece. With such a force irregularities in the surface of the workpiece tend to shift or rotate the marking wheels from their desired preselected positions. This sometimes results in damaging or even breaking the pawl, teeth of the cogwheel or other parts of the marking head.
Sometimes the marking wheel is rotated by this force sufficiently from its desired position so that a subsequent actuation of the pawl does not advance the marking wheel to the proper position to select the desired symbol for the next marking operation. Furthermore, if the marking wheel is rapidly indexed it occasionally overshoots or rotates farther than is desired and hence does not correctly position the desired symbol for the next marking operation.